Electric incandescent lamps

ABSTRACT

A tungsten-halogen cycle electric incandescent lamp contains a solid aromatic halide in the fill which dissociates when the lamp is heated to provide halogen to support the regenerative cycle. The aromatic halide can be hexabromobenzene or hexachlorobenzene and the fill may also include a halophosphonitrile.

United States Patent [1 1 Ree-s et al. .May 14, 1974 154] ELECTRIC INCANDESCENT LAMPS 3,738,729 6/1973 Coxon et al. 313 222 [76] Inventors: John Michael Rees; George Eric g z tfi g Bemgd g Primary Examiner-Herman Karl Saalbach E f s gs Assistant Examiner-Darwin R. Hostetter at m S on on Attorney, Agent, or Firm-Kemon, Palmer and England Estabrook [22] Filed: May 29, 1973 [21] App]. No.: 364,917

Related U.S. Application Data [57] ABSTRACT [63] Continuation-impart of Ser. No. 317,813, Dec. 22,

1972, abandoned. A tungsten-halogen cycle electric incandescent lamp contains a solid aromatic halide in the fill which disso- [52] U.S. Cl. 313/222, 316/20 ciates when the lamp is heated to provide halogen to [51] Int. Cl. H011: l/50, HOlk 3/00 support the regenerative cycle. The aromatic halide [58] Field of Search 313/222; 316/20 can be hexabromobenzene or hexachlorobenzene and the fill may also include a halophosphonitrile. [56] References Cited UNITED STATES PATENTS 11 Claims, 3 Drawing Figures 3,712,701 l/l973 Johnson et al 313/222 1 ELECTRIC INCANDESCENT LAMPS This application is a continuation-in-part of our application Ser. No. 317,813 filed Dec. 22nd, 1972, now abandoned.

The present invention relates to tungsten-halogen electric incandescent lamps.

Such lamps have a tungsten filament enclosed within a light-transmitting envelope containing a fill of nonreactive gas, such as N Ar, Kr or Xe and a small quantity of halogen, for example iodine.

The simplified mechanism of the reactions occurring during operation of such a lamp is that tungsten escaping from the incandescent filament, which would normally diffuse to the bulb wall,'reacts with the iodine to form tungsten iodide. When the tungsten iodide diffuses into the high temperature zone surrounding the filament it dissociates, liberating the tungsten and iodide. This regenerative cycle effectively prevents radial diffusion of tungsten and the bulb wall remains clean throughout life. Consequently, bulb surface area is not important in a lamp where a regenerative cycle is operating and this allows very compact lamps with mechanically strong tubular fused silica envelopes to be used, so permitting filling to a pressure of several atmospheres, which gives improved filament life.

More recently, bromine has been used in place of iodine but while this eliminated the characteristic mauve tinge caused by the selective absorption of molecular iodine, it was found that precise control was required to avoid reaction between excess bromine and solid tungsten. It was shown that this reaction could be inhibited by introducing'hydrogen, and HBr, CHBr CH Br and CH Br were suggested as a suitable means of transporting hydrogen and bromine into a lamp, but this has the disadvantage that diffusion of hydrogen through fused silica may result in an excess of free bromine in a lamp during its life, which causes tungsten erosion and eventual failure. In consequence it is usual to employ iodine in long life lamps (above 1,000 hours) and bromine, admitted as a hydrogen-containing compound, in shorter life lamps.

The disadvantage of gaseous halogen dosing, and in particular the use of hydrogen-containing halides, was discussed in US Pat. application Ser. No. 1404, now abandoned which proposed the use of halophosphonitriles as a halogen source. I It has now been found, according to the present invention, that solid aromatic organic halides represent a useful means of introducing halogen into a tungstenhalogen incandescent lamp. Suitable aromatic halides have a low vapour pressure and preferably introduced into the lamp envelope as a solution in a volatile nonpolar solvent, such as petroleum-ether (especially 6080 C b pt), ether, and cyclic, aromatic or chlorinated hydrocarbons, e.g. benzene which is removed from the lamp by evacuation or by flushing with a dry non-reactive gas, (e.g. nitrogen).

Of particular interest for the purposes of this invention are hexahalogenated benzenes, and especially hexabromobenzene and hexachlorobenzene.

Dosing with hexachlorobenzene has been found to be particularly useful with short life film projection lamps having an operational filament temperature of more than 3,000 K and a life of up to 100 hr.

The advantages of the use of solid aromatic halides include accuracy and repeatability of dosing, relative insensitivity to moisture and the reduction, and in some cases elimination, of hydrogen from the cycle.

Tungsten-halogen lamps in accordance with the invention will now be more fully described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 shows a completed two-ended tungstenhalogen lamp; and

FIGS. 2 and 3 show a single-ended lamp and a U- shaped lamp, respectively, in the course of manufacture.

Referring to the accompanying drawings, like reference numerals indicate similar portions of the lamps.

In each of the lamps shown, there is a quartz envelope l surrounding a tungsten filament 2, with lead-in wires 4, which are press-sealed through the ends of the envelope 1, for supplying electrical current to the filament 2.

In the lamp shown in FIG. 1, the filament 2 is mounted on filament supports 3 within the envelope 1, and the ends of the lamp have contact members 5 connected to the lead-in wires 4. The envelope 1 contains nitrogen, carbon and a halogen the carbon and halogen having been formed by the thermal dissociation of a solid aromatic halide, e.g. a hexahalogenated benzene within the lamp envelope 1.

In the lamps shown in FIGS. 2 and 3 the filament 2 is connected to electrically conductive foils 6 presssealed within the material of the lamp envelope 1, and the foils 6 are in turn connected to the lead-in wires 4. The envelopes 1 each have exhaust tubes 7 connected thereto, giving access to the interior of the envelope.

In FIG. 3, the lamp has within the envelope 1 filament supports 3 on which the filament 2 is mounted.

Examples of methods of making lamps according to the invention will now be described.

A typical example of the practice of this invention is the dosing with hexabromobenzene of'a 12V 55W single end automobile lamp of the type shown in FIG. 2. The needle ofa hypodermic syringe is inserted into the unsealed exhaust tube 7 of the lamp, and 0.025 cm of a solution containing 0.05g of hexabromobenzene in cm of benzene is injected into the envelope 1. The solvent is removed by flushing with a stream of dry nitrogen (preferably containing less than 10 ppm of water vapour) passed through the exhaust tube 7, after which the envelope 1 is exhausted and gasfilled with a non-reactive gas such as N Ar, Kr or Xe in the usual manner, and the exhaust tube 7 is sealed off. On operation of the lamp, or otherwise raising it to a high temperature, the hexabromobenzene dissociates to yield bromine for supporting the regenerative cycle.

In a further example, a 12V, 100W single-ended projection lamp of the type shown in FIG. 2, having a nominal efficiency of 30 lm/W and a rated life of 25 hours, is produced using hexachlorobenzene as the dosing substance. The needle of a hypodermic syringe is inserted into the unsealed exhaust tube 7 of the lamp, and 0.05 cm of a solution containing 0.04g of hexachlorobenzene in 100 cm of toluene is injected into the envelope 1. The solvent is then removed by flushing with a stream of dry nitrogen with the bulb temperature raised to 100 C to speed up the extraction process. After this the envelope is exhausted and gasfilled with a nonreactive gasfilling in-the usual manner.

A further advantage of aromatic halides is that they are compatible with halophosphonitriles (the use of phorus to halogen to be regulated to suit the particular lamp, or a mixture of halogens tobe added in accurately controlled proportions.

One example of this aspect of the invention is in the production of a 240V 1,000W photographic U-lamp type of the type shown in FIG. 3. Such a lamp can be made by dispensing 0.05 cm of a solution containing 0.lg of bromophosphonitrile and 0.1g of hexabromobenzene in 100 cm of benzene into the lamp by way of the exhaust tube 7. Again, the'solvent is removed by flushing with a stream of dry nitrogen followed by exhaustion and gas-filling with a non-reactive gas.

We claim:

1. A tungsten-halogen cycle electric incandescent lamp comprising: a light-transmitting, high tempei'ature-resisting envelope; a tungsten filament within said envelope; lead-in wires sealed through said envelope and connected to said filament; and a fill within said envelope capable of supporting a tungsten-halogen regenerative cycle in co-operation with said filament, said fill comprising a non-reactive gas, carbon, and a halogen, said carbon and halogen having been formed by dissociation ofa solid aromatic halide within said envelope.

2. A lamp as claimed in claim 1 wherein said fill includes hydrogen formed by dissociation of said halides.

3. A tungsten-halogen cycle electric incandescent matic halide.

4. A lamp as claimed in claim 1 wherein said carbon, and halogen have been formed by dissociation of a ha- .logenated benzene.

5. A lamp as claimed in claim 4 wherein said halogenated benzene is a hexahalogenated benzene.

6. A lamp as claimed in claim 5 wherein said hexahalogenated benzene is hexabromobenzene.

7. A lamp as claimed in claim 5 wherein said hexahalogenated benzene is hexachlorobenzene.

8. A lamp as claimed in claim 1 wherein said fill includes a halogen, phosphorus and nitrogen formed by dissociation of a halophosphonitrile within said envelope.

9. A method of making a tungsten-halogen cycle electric incandescent lamp comprising the steps of:

providing a light-transmitting high-temperature resisting envelope having an aperture therein, a tun gsten filament therewithin, and lead-in wires connected to said filament and sealed therethrough; introducing a normally solid aromatic halide into said envelope through said aperture; exhausting said envelope; gas-filling said envelope with a nonreactive gas; sealing said aperture; and raising said envelope to a high temperature sufficient to dissociate said aromatic halide.

10. A method as claimed in claim 9 wherein a solution of a solid aromatic halide in a volatile non-polar solvent is introduced into said envelope, said solvent being volatilised from said envelope before said gasfilling step.

11. A method as claimed in claim 9 wherein said solvent is selected from the group consisting of petroleum ether; cyclic hydrocarbons; aromatic hydrocarbons and chlorinated hydrocarbons.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,811,063 Dated y 1974 Inventods) John Michael Rees, George Eric Coagon, Robert Bernard Johnston It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data Great Britain H 274 08/72 June 12, 1972 Signed and sealed this 10th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 v: u,s, govzmmsu'r PRINTING OFFICE: 19 o-asa-su,

FORM FO-1050(10-69) 

2. A lamp as claimed in claim 1 wherein said fill includes hydrogen formed by dissociation of said halides.
 3. A tungsten-halogen cycle electric incandescent lamp comprising: a light-transmitting high temperature-resisting envelope; a tungsten filament within said envelope; lead-in wires sealed through said envelope and connected to said filament; and a fill within said envelope comprising a non-reactive gas and a solid aromatic halide.
 4. A lamp as claimed in claim 1 wherein said carbon, and halogen have been formed by dissociation of a halogenated benzene.
 5. A lamp as claimed in claim 4 wherein said halogenated benzene is a hexahalogenated benzene.
 6. A lamp as claimed in claim 5 wherein said hexahalogenated benzene is hexabromobenzene.
 7. A lamp as claimed in claim 5 wherein said hexahalogenated benzene is hexachlorobenzene.
 8. A lamp as claimed in claim 1 wherein said fill includes a halogen, phosphorus and nitrogen formed by dissociation of a halophosphonitrile within said envelope.
 9. A method of making a tungsten-halogen cycle electric incandescent lamp comprising the steps of: providing a light-transmitting high-temperature resisting envelope having an aperture therein, a tungsten filament therewithin, and lead-in wires connected to said filament and sealed therethrough; introducing a normally solid aromatic halide into said envelope through said aperture; exhausting said envelope; gas-filling said envelope with a non-reactive gas; sealing said aperture; and raising said envelope to a high temperature sufficient to dissociate said aromatic halide.
 10. A method as claimed in claim 9 wherein a solution of a solid aromatic halide in a volatile non-polar solvent is introduced into said envelope, said solvent being volatilised from said envelope before said gas-filling step.
 11. A method as claimed in claim 9 wherein said solvent is selected from the group consisting of petroleum ether; cyclic hydrocarbons; aromatic hydrocarbons and chlorinated hydrocarbons. 